Shock resistant, high reliability rotating magnetic storage device and method

ABSTRACT

An information recording method in a rotating storage apparatus comprising a rotating recording medium for recording information, a head for performing at least a write operation onto the rotating recording medium, and an acceleration sensor for detecting a shock. The method comprises outputting a shock out signal if an output from the acceleration sensor exceeds a predetermined threshold. A signal is output at a first level during a write inhibit period in response to the input of the shock out signal, where the write inhibit period is selected based at least in part on a time span in which the output of the acceleration sensor exceeds the predetermined threshold. Writing to the rotating recording medium is prohibited during the write inhibit period.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.10/793,318 to Kisaka et al., filed Mar. 3, 2004, which is a continuationof U.S. patent application Ser. No. 09/813,081 to Kisaka et al., filedMar. 19, 2001 and now U.S. Pat. No. 6,754,021.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rotating storage apparatus andinformation recording method, and in particular, to protective measuresagainst shock and vibration during the operation of information storageapparatus in which information is recorded on a rotating recordingmedium such as a hard disk.

2. Description of the Background Art

In recent years, information processing systems have been widely used inportable devices such as notebook personal computers. In portabledevices, vibration and shock are unavoidable and protective measuresagainst vibration and shock have become important. Improvement of shockresistance is a very important especially in a storage apparatuscontaining a rotating recording medium such as a hard disk because ithas a moving mechanism for changing relative positional relationshipbetween a head having read/write capability and the rotating medium.

As is known to those skilled in the art, tracks are provided on arotating recording medium (hard disk) in hard disk drive, for example,and a head is positioned over a track to record a magnetic signal fromthe head in the track. If the head underwent external shock or vibrationwhile the head is positioned over a track and information from the headis being recorded (written) in the track, the head would go off thepredetermined track (off-tracking) and the information would be writtenin a position at a distance from the predetermined track. Theinformation written in such an off-tracking condition may not only causea read error but also, if information has been recorded in adjacenttracks, affect the adjacent tracks to prevent the information from beingrecorded correctly.

Examples of approaches for preventing information recording in anoff-tracking condition includes a technology described in PublishedUnexamined Patent Application No. 1-126412(Japan). The technology isdescribed in that application which has the object of improving theperformance of a rotating recording apparatus in an environment in whichthe apparatus undergoes a shock. In particular, the timing control isoptimized for a retry operation according to the affecting magnitude ofshock force or vibration. An optimum retry interval is set according tothe magnitude of the shock or vibration from retry intervals stored inmemory to cause a data write operation to be retried with an optimumtiming if the shock or vibration is detected to halt the writeoperation. In this way, the number of retries or wasteful latency couldbe reduced compared with the case where a fixed retry latency isdetermined, thereby improving the performance of the apparatus.

However, the technology described in that application and otherprior-art technologies have the following problems. A gravitationalacceleration sensor (G-sensor) is used to detect a shock and vibration.The physical quantity detected by the G-sensor is acceleration(proportional to force) and does not exactly reflect the off-trackingamount described above. The off-tracking amount is a displacement(position) from an intended track position at which a head is to bepositioned. Although a shock or vibration (force) causes thedisplacement of the head and therefore off-tracking, an output from theG-sensor does not directory represent the off-tracking amount. Because aposition is typically represented by the double integral of force in asystem in which a feedback is provided, such as the head positioningcontrol system of a hard disc drive, an actual off-tracking amount isprovided with time delay with respect to the output of the sensor. As aresult, a problem arises if a pulse-like shock that is as short as thetime delay is exerted, as described below. This problem will bedescribed with reference to FIG. 6.

FIG. 6A shows a logic circuit diagram for explaining the problem. FIG.6B shows a diagrammatic drawing. As shown in FIG. 6A, a shock outputsignal 101 (called a shock out), which is present if an output from theG-sensor exceeds a predetermined threshold, is referenced when a writegate signal 102 is asserted (goes high). When both of the shock outsignal 101 and the write gate signal 102 are high, the output of an ANDcircuit 103 goes high and is latched by a latch circuit 104 for apredetermined time period and a write inhibit signal is generated. Thewrite inhibit signal is inverted by a NOT circuit 105 and input to anAND circuit 106 to mask the write gate signal 102 (force it low). Thisinhibits the write operation. In other words, the shock out signal 101is referenced only when the write gate is open and the write inhibitsignal is not generated when the write gate is closed (the write gatesignal 102 is low).

This will be described in time sequence with reference to FIG. 6B. Curve110 is a waveform representing, with respect to the time-axis, an outputfrom the G-sensor when a short pulse shock is exerted. The shock outsignal 101 is continuously output in the output waveform of curve 110while a threshold 111 is exceeded. However, unless the write gate signal102 is asserted (high), no write inhibit signal is generated, asdescribed above. Here, no problem would occur if the phase of thewaveform 110 of the sensor output matches that of off-tracking amount atthe position of the head. However, an actual off-tracking at the headposition is delayed with respect to the sensor output waveform of curve110 as shown by curve 113. If the write gate signal 102 is asserted(high) at time t2 immediately after the time (t1) at which the shock outsignal 101 stops, no write inhibit signal would be generated and a writeoperation start because the shock out signal 101 is not high even thoughthe head position is off-track.

The inventors of the present invention have found that theabove-mentioned problem was likely to arise when a hard disk drive isinstalled in a portable computer, which in turn is particularlysusceptible to an external shock and vibration. Also the problem is morepronounced as the recording density increases. For example, theabove-mentioned problem is likely to occur when the storage density isincreased to about 30 ktpi or over in a typical hard disk drive of 4,200rpm.

What is needed is a disk drive with more robust resistance to shockdisturbances.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an apparatus andmethod of achieving high recording reliability of a rotating storageapparatus which uses a high-density storage medium, even in anenvironment where a shock or vibration exists. It is another object ofthe present invention to provide an apparatus and method that caninhibit a write operation in an off-tracking condition even in anenvironment where a short pulse shock or high-frequency vibration isexerted. It is yet another object of the present invention to provide anapparatus and method for an optimum write inhibit according to themagnitude of a shock or the amplitude of vibration and that can increasethe writing speed as well as the reliability of the apparatus to improvethe performance of the apparatus.

The outline of the present invention will be described below. Therotating storage apparatus of the present invention comprises a rotatingrecording medium for recording information, a head for performing atleast a write operation onto the rotating recording medium, and anacceleration sensor for detecting a shock. If an output from theacceleration sensor exceeds a predetermined threshold, the writeoperation is inhibited during a predetermined write inhibit periodregardless of the status of a write gate signal.

The rotating storage apparatus of the present invention comprises arotating recording medium for recording information, a head forperforming at least a write operation onto the rotating recordingmedium, and an acceleration sensor for detecting a shock. The apparatuscomprises 1) means for monitoring an output from the acceleration sensorand, if the monitor output exceeds a predetermined threshold, outputtinga shock out signal 2) latch means for outputting a latch signal at afirst level during a predetermined write inhibit period from a time atwhich the shock out signal is input 3) write gate signal generationmeans for outputting the signal at the first level when a writepermission is given and 4) a logic enabling a write onto the rotatingrecording medium when the latch signal is at a second level other thanthe first level and when the write gate signal is at the first level.

The information recording method of the present invention is a methodfor recording information in a rotating storage apparatus comprising arotating recording medium for recording information, a head forperforming at least a write operation onto the rotating recordingmedium, and an acceleration sensor for detecting a shock. The methodcomprises 1) outputting a shock out signal if an output form theacceleration sensor exceeds a predetermined threshold 2) outputtingcontinuously a signal at a first level during a predetermined writeinhibit period in response to the input of the shock out signal 3)generating a logical AND signal of a logical negation signal at a firstlevel and a write gate signal output, the write gate signal becomes thefirst level when a write permission is given and 4) enabling a writeonto the rotating recording medium when the logical AND signal is at thefirst level.

According to the above-described rotating storage apparatus orinformation recording method, a write inhibit signal is generated at thetime when a shock out signal is detected, regardless of the status ofthe write gate. The write inhibit signal is referenced and if theapparatus is in the write inhibit state, a write gate signal is masked(negated, goes low). The period (write inhibit period) during which thewrite inhibit signal is continuously output after the shock out signalis detected is predetermined by taking the characteristics of theapparatus into account, and in addition, changed by referencing thewidth of the output signal or the peak value of the acceleration sensor.This ensures that the write inhibit signal is generated to inhibit awrite operation in an off-tracking condition whenever the head is in theoff-tracking condition in an environment in which a short pulse-likeshock or high-frequency vibration is exerted on the apparatus. Thus, theinformation recording reliability of the apparatus can be increased. Inaddition, the write time can be reduced by selecting an optimum writeinhibit duration, thereby improving the performance of the apparatus.

High recording reliability of a rotating storage medium apparatus usinga high-density recording medium can be achieved even in an environmentwhere a shock or vibration exists.

A write operation in an off-tracking condition can be inhibited even inan environment where a short pulse shock or high-frequency vibration maybe exerted.

An optimum write inhibit operation can be performed according to themagnitude of a shock or the amplitude of vibration, thus improving thewriting speed and performance as well as the reliability of theapparatus.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example of a hard disk drive of anembodiment of the present invention.

FIG. 2 is a block diagram showing an example of the hard disk drive ofthe embodiment of the present invention.

FIG. 3 is a circuit block diagram showing part of a hard diskcontroller.

FIG. 4 is a chart showing the timing of outputs from major parts of thecircuit, the waveform of outputs of an acceleration sensor, anoff-tracking amount.

FIG. 5 is a block diagram showing a circuit for 5 determining a changeof write inhibit period.

FIG. 6A is a logic circuit diagram of the prior art.

FIG. 6B is a chart for explaining the prior art.

DETAILED DESCRIPTION OF THE INVENTION

An embodiment of the present invention will be described below withreference to the accompanying drawings. However, the present inventionmay be implemented in many different embodiments and should not beconstrued as being limited to the description of the embodiment.Throughout the description of the embodiment, like elements are labeledwith like numbers.

FIG. 1 is a perspective view showing an example of a hard disk drive,which is one embodiment of the present invention. FIG. 2 is a blockdiagram of the hard disk drive. The hard disk drive of this embodimentcomprises a disc-like magnetic recording medium 1 on which informationis magnetically recorded, a spindle motor 2 for driving the magneticrecording medium 1, a magnetic head 3 for recording information on themagnetic recording medium 1 or reading from information recorded on themagnetic recording medium 1, an arm 4 for supporting the magnetic head3, a voice coil motor 5 for driving the arm 4, and a hard diskcontroller 6 for controlling input and output of information into andfrom the magnetic head 3 and the drive of the spindle motor 2 and voicecoil motor 5. Data writing and reading to and from the magnetic head 3are performed through a flexible cable 8 attached to a connector 7 andthe arm 4. A gravitational acceleration sensor 9 is attached to theflexible cable 8. While the gravitational acceleration sensor 9 is shownas attached to a movable part of the flexible cable 8 in FIG. 1 forclarity, it is in practice attached to a cable connection part in theclose proximity of the connector 7 so that vibration of the cable is notdetected by the gravitational acceleration sensor 9.

The hard disk controller 6 interfaces to a host computer 10 and reads orwrites information from or onto the magnetic recording medium 1 asmagnetic information, according to a read or write request from the hostcomputer 10. FIG. 3 is a circuit block diagram of part of the hard diskcontroller 6. FIG. 4 shows a chart of the output timing from major partsof the circuit and the waveform of outputs from the gravitationalacceleration sensor and the off-tracking amount of the head.

The circuit block shown in FIG. 3 consists of a latch 5 circuit 21 forlatching a shock out signal SO, a NOT circuit 22 for negating the outputfrom the latch circuit 21, and an AND circuit 23 to which the outputfrom the NOT circuit 22 and a write gate signal WG are provided as itsinputs.

FIG. 4A is a chart showing the waveform of an output 10 from thegravitational acceleration sensor 9 in response to a shock exerted onthe drive apparatus. It is assumed that waveform 30 as shown is outputwhen a short pulse shock is exerted. An output (shock out signal SO) 33as shown in FIG. 4B is continuously output from the sensor during thetime period in which the waveform 30 exceeds a predetermined threshold31. The displacement (off-tracking amount) from a track position of themagnetic head 3 caused by this shock is indicated by curve 34 in FIG.4C. The off-tracking amount (curve 34) is a physical quantity having adistance dimension and represented by a double integral as mentionedearlier, and therefore has time delay with respect to the sensor output(waveform 30)

According to the present invention, a write inhibit signal 35 isgenerated as shown in FIG. 4D in order to inhibit a write operationwhile such off-tracking exists. The write inhibit signal 35 is generatedby the circuit block shown in FIG. 3. That is, the shock out signal SOis generated by shock out generating means (not shown) and input intothe latch circuit 21. The output of the latch circuit 21 is held highduring a predetermined time period after time t3 at which the shock outsignal SO is detected (write inhibit period (t4−t3). The output signalfrom the latch circuit 21 is converted into low by the NOT circuit 22.In other words, during the write inhibit period, a low-level signal isinput into the AND circuit 23 and the output from the AND signal 23 goeslow regardless of the status of the write gate signal WG to keep thewrite inhibit state.

In this way, according to the present invention, a write operation isinhibited during a predetermined period(write inhibit period) after ashock out signal SO is detected, regardless of the status of the writegate WG. Thus, the write inhibit state can be kept to inhibit a writeoperation in an off-tracking condition even if a short pulse shock isexerted.

As shown in FIG. 4E, the output 36 (final write gate output) from theAND circuit 23 does not continuously go high (asserted) even if thewrite gate (WG) is asserted (goes high) at time t5 during the writeinhibit period, and goes high (asserted) at time t6 by a retry after theend of the write inhibit period. The asserted state (high level) of thewrite gate signal 36 forces a write signal 37 onto the magneticrecording medium 1 to be output. Examples of the write signal 37includes a synchronous signal, address signal, user data signal, anderror correction code signal. The write inhibit period (t4−t3), that is,a latch period by the latch circuit 21, can be fixed in appropriate timeperiods by analyzing the variation characteristics of the arm 4 andother components beforehand by experiments and reflecting the results ofthe experiments in the determination. It has been empirically found thata period equivalent to 15 servo sectors is appropriate. Because thesampling frequency for one servo sector is 5.6 kHz, about 2.7 msec maybe appropriate.

The write inhibit period may be varied in consideration of an outputvalue from the gravitational acceleration sensor 9. FIG. 5 is a blockdiagram showing an example of a circuit for determining a change ofwrite inhibit period. This circuit is contained in the hard diskcontroller 6, for example.

An output signal (Sig) from the gravitational acceleration sensor 9 isinput into an amplifier (AMP) 40. The output of the AMP 40 is input intoa window comparator 41 and an analog-digital converter (ADC) 42. Thewindow comparator 41 outputs the high-level signal when a signalexceeding a predetermined threshold is input. The time span in which theoutput is held high is measured by a pulse width measurement circuit 43.The measured value is input into a micro processing unit (MPU) 44, wherea write inhibit period is calculated according to the time span measuredby the pulse width measurement circuit 43. A controller MPU installed ina hard disk controller 6 may also be used as the MPU 44.

On the other hand, a signal converted into a digital 10 signal in theADC 42 is input into the MPU 44 and the largest value (the peak value ofthe signal) is selected and a write inhibit period according to the peakvalue is calculated in the MPU 44.

The write inhibit period calculated in the MPU 44 can be input into thelatch circuit 21 in FIG. 3 and the write inhibit period is set as thelatch period. In this way, the write inhibit period can be variedaccording to the signal width or peak value of the gravitationalacceleration sensor 9, thereby allowing an optimum write inhibit periodto be set according to the output value of the gravitationalacceleration sensor 9 by a program provided to the MPU 44. Of course,findings in experiments and studies can be reflected in the optimizationof this program.

Any methods that take into account only the pulse width value, only thepeak value, or both of the pulse width and peak value may be used forthe calculation of the write inhibit period by the MPU 44.

While the present invention by the inventors has been described inparticular with respect to the embodiment of the present invention, thepresent invention is not limited to the above-described embodiment.Various changes may be made to the present invention without departingfrom the scope and spirit of the present invention. For example, whilethe embodiment has been described with respect to the hard disk drive asan example of the rotating storage apparatus, the present invention isnot limited to the hard disk drive. Instead, the present invention maybe applied to any storage apparatus having a rotating recording medium,including a rewritable optical and magneto-optical recording apparatussuch as CD-R/W, DVD, and MO drive storage apparatuses. In addition, thepresent invention may be applied to a removable rotating magneticrecording apparatus.

Any acceleration sensors, including a dielectric sensor such as agyro-meter, and a semiconductor sensor may be used as the accelerationsensor 9. In addition, while the example in which the time span and peakvalue of the sensor output are referenced to vary the write inhibitperiod has been described, the sensor output waveform may be analyzed byusing an appropriate method such as fast-Fourier-transform processingand the result of the analysis may be used to calculate the writeinhibit period more precisely.

1. An information recording method in a storage apparatus comprising arotating recording medium for recording information, a head forperforming at least a write operation onto the rotating recordingmedium, and an acceleration sensor for detecting a shock, the methodcomprising: outputting a shock out signal if an output from theacceleration sensor exceeds a predetermined threshold; outputting asignal during a write inhibit period in response to the input of theshock out signal, wherein the write inhibit period is selected based atleast in part on a time span in which the output of the accelerationsensor exceeds the predetermined threshold; and prohibiting writing tothe rotating recording medium while the signal is being output duringthe write inhibit period.
 2. A method as recited in claim 1, wherein thewrite inhibit period is further based at least in part based on anoutput peak value of the acceleration sensor.
 3. A method as recited inclaim 1, further comprising generating a logical AND signal of a logicalnegation signal of the signal at a first level and a write gate signaloutput, the write gate signal output being at the first level when awrite permission is given; and enabling a write onto the rotatingrecording medium when the logical AND signal is at the first level.
 4. Amethod as recited in claim 1, wherein the write inhibit period is longerthan a period that the output from the acceleration sensor exceeds thepredetermined threshold.
 5. A method as recited in claim 1, wherein thewrite inhibit period is selected by varying a predetermined fixed timeperiod based at least in part on the time span in which the accelerationsensor output exceeds the threshold.
 6. A method as recited in claim 1,wherein the write inhibit period is further selected by varying apredetermined fixed time period based at least in part on the peak valueof the acceleration sensor output.
 7. A method as recited in claim 1,wherein the acceleration sensor is selected from a group consisting of agravitational acceleration sensor, a gyro-meter, and a semiconductorsensor.
 8. A method as recited in claim 1, wherein the storage apparatusis a hard disk drive.
 9. A method as recited in claim 1, wherein thestorage apparatus is removable from a host system.
 10. A method asrecited in claim 1, wherein the rotating recording medium is an opticaldisk.
 11. An information recording method in a data storage apparatus,comprising: performing at least a write operation onto a recordingmedium; receiving output from an acceleration sensor, the accelerationsensor output indicating that a shock has been detected; outputting alatch signal at a first level during a write inhibit period, wherein thewrite inhibit period is selected based on the acceleration sensoroutput; outputting a write gate signal at the first level when a writepermission is given; and enabling a write onto the recording medium whenthe latch signal is at a second level other than the first level andwhen the write gate signal is at the first level.
 12. A method asrecited in claim 11, wherein the write inhibit period is selected basedat least in part on a time span in which the acceleration sensor outputexceeds a predetermined threshold.
 13. A method as recited in claim 11,wherein the write inhibit period is selected based at least in part on apeak value of the acceleration sensor output.
 14. A method as recited inclaim 11, wherein the write inhibit period is further selected based atleast in part on a waveform of the acceleration sensor output.
 15. Amethod as recited in claim 11, wherein the write inhibit period islonger than a period that the output from the acceleration sensorexceeds the predetermined threshold.
 16. A method as recited in claim11, wherein the write inhibit period is selected by varying apredetermined fixed time period based at least in part on the time spanin which the acceleration sensor output exceeds the threshold.
 17. Amethod as recited in claim 11, wherein the write inhibit period isfurther selected by varying a predetermined fixed time period based atleast in part on the peak value of the acceleration sensor output.
 18. Amethod as recited in claim 11, wherein the acceleration sensor isselected from a group consisting of a gravitational acceleration sensor,a gyro-meter, and a semiconductor sensor.
 19. A method as recited inclaim 11, wherein the storage apparatus is a hard disk drive.
 20. Amethod as recited in claim 11, wherein the storage apparatus isremovable from a host system.
 21. A method as recited in claim 11,wherein the recording medium is an optical disk.
 22. An informationrecording method in a storage apparatus comprising a head for performingat least a write operation onto a recording medium, and an accelerationsensor for detecting a shock, the method comprising: receiving an outputfrom the acceleration sensor; determining whether the accelerationsensor output exceeds a predetermined threshold; if the accelerationsensor output exceeds the predetermined threshold, determining a timespan in which the output of the acceleration sensor exceeds thepredetermined threshold; selecting a write inhibit period based at leastin part on the time span in which the output of the acceleration sensorexceeds the predetermined threshold; and prohibiting writing to therecording medium during the write inhibit period.